Synergistic design of a molten salt-exfoliated CuS/C3N4 heterojunction: elucidating photogenerated charge transfer behavior and mechanism for enhanced photocatalytic hydrogen evolution

Abstract

Photocatalytic hydrogen production using carbon nitride semiconductors is an effective strategy for mitigating energy and environmental challenges. However, their low specific surface area and high recombination rate of photogenerated carriers limit their photocatalytic activity. Herein, we employed a LiCl/KCl molten salt approach to enhance the specific surface area of carbon nitride and obtain (C₃N₄(Li–K)). The CuS/C₃N₄(Li–K) heterojunction was then constructed with CuS, leveraging their well-matched energy bands. This heterojunction enables directional charge separation. Photogenerated electrons are transferred from the conduction band of C₃N₄(Li–K) to CuS, while holes migrate from CuS to the valence band of C₃N₄(Li–K). Additionally, CuS's excellent electron transport capability promotes surface electron transfer during catalytic reactions. Consequently, the CN/CuS-3 composite achieves a hydrogen evolution activity of 640 μmol g⁻¹ h⁻¹, which is 2.9 times higher than that of C₃N₄(Li–K).